Wednesday, October 31, 2007

A Consciousness Debate

Christof Koch and Susan Greenfield offer a written version of their Oxford University Debate in the summer of 2006 in the Oct. 2007 issue of Scientific American. While they make a point of contrasting their models of the neuronal correlates of consciousness, I think a blending of the two may most closely approach the real situation.

What happens in your brain when you see a dog, hear a voice, suddenly feel sad or have any other subjective experience?

KOCH'S MODEL
A coalition of pyramidal neurons linking the back and front of the cortex fires in a unique way. Different coalitions activate to represent different stimuli from the senses (left). In a mouse cortex (right) these pyramidal cells (green) lie in brain layer 5, surrounded by nonneuronal cells (blue).


GREENFIELD'S MODEL
Neurons across the brain fire in synchrony (green) and prevail until a second stimulus prompts a different assembly to arise (orange). Various assemblies coalesce and disband moment to moment, while incorporating feedback from the body. In a rat brain (bottom), an assembly in the cortex forms (a, b), peaks (c), then decays (d) within 0.35 second after the thalamus is electrically stimulated.

Christof Koch is professor of cognitive and behavioral biology at the California Institute of Technology, where he teaches and has conducted research on the neuronal basis of visual attention and consciousness for more than two decades.

Susan Greenfield is professor of pharmacology at the University of Oxford, director of the Royal Institution of Great Britain and member of the British Parliament's House of Lords. Her research focuses on novel brain mechanisms, including those underlying neurodegenerative diseases.

A new consiousness and philosophy of mind bibliography

David Chalmers and David Bourget are offering a more extensive online service, outlined in this message from ASSC (Assoc. for Sci.Stud. Cons.):

We are pleased to announce the launch of MindPapers, a new website
with a bibliography covering around 18000 published papers and online
papers in the philosophy of mind and the science of consciousness.
This site grew out of a combination of David Chalmers' bibliography in
philosophy of mind and his page of online papers on consciousness, but
it is much larger and has many new capacities, programmed by David
Bourget. The site address is:

http://consc.net/mindpapers/

There is also a separate front end for "Online Papers on
Consciousness". Where MindPapers now combines both offline published
papers and online papers from free and commercial sites, Online Papers
on Consciousness is devoted to free online papers (currently around
4700). It is based on the same database as MindPapers, but is
organized in a way to emphasize issues concerning consciousness and
cognitive science rather than the philosophy of mind. The address is

http://consc.net/online/

The MindPapers database contains 2773 papers on the philosophy of
consciousness (under 59 topics and subtopics) and 3917 papers on the
science of consciousness (under 71 topics and subtopics), as well as
thousands of papers on such related topics as perception,
intentionality, the philosophy of AI, and the philosophy of cognitive
science.

Capacities include (i) links and citation information throughout, (ii)
flexible navigation, display, and search options, (iii) the ability to
submit and edit entries, (iv) the capacity for automated off-campus
proxy access to commercial sites, and (v) a wealth of statistical
information.

We encourage everyone to try these sites to submit any relevant
material that we are missing (for a start, try searching on your own
name). There are tools on the site for submitting entries, as well as
for correcting entries and notifying us of any bugs and suggestions.

--David Chalmers and David Bourget
chalmers@anu.edu.au; david.bourget@anu.edu.au

Tuesday, October 30, 2007

Sleep deprivation diminishes recall of neutral and positive, but not of negative, events.

We remember emotional events, particularly negative ones, better than neutral events. Sterpenich et al. show that while consolidation of neutral and posititive memories is diminished by sleep deprivation, recall of negative events is less compromised. They show that after sleep deprivation, recollection of negative, potentially dangerous, memories recruits an alternate amygdalo-cortical network, which would keep track of emotional information despite sleep deprivation. Here is their description of the work:

Declarative memories, which can be consciously and verbally retrieved, are initially critically dependent on the hippocampus. However, reliable retrieval of long-term memory depends on a process of consolidation, which partly occurs during sleep, when memories are thought to be progressively transferred to long-term cortical stores. Because people tend to remember emotional memories better than neutral ones, we wondered whether the emotional significance of a memory would enhance its consolidation in a sleep-dependent manner. During a first session, participants viewed pictures with neutral and emotional content without realizing that their memory of the pictures and their content would be tested later (called incidental encoding). Three days later, during a functional MRI scanning session, subjects indicated whether they recognized previously viewed and new pictures. Half of the subjects were totally sleep deprived during the first post-encoding night, but all subjects slept as usual during the second and third post-encoding nights. We show here that the recollection of emotional stimuli elicited larger responses in the hippocampus and various cortical areas in the well-rested group than in the sleep-deprived group, suggesting that emotional significance boosts memory consolidation of the information during sleep. Interestingly, in sleep-deprived subjects, recollection of negative items recruited another network including the amygdala, as if an alternate consolidation process allowed them to keep track of negative, potentially dangerous, information despite the cognitive aftermath of sleep deprivation.

Biology and Health Inequality

PLoS Biology has ventured beyond its usual fare to publish several articles focusing on poverty, human development, and the environment. This article is from Eric Brunner. He points out several studies that demonstrate a direct psychosocial pathway to disease. It's precis: "Intriguing parallels between civil servant and nonhuman primate hierarchies suggest that highly stratified societies foster health inequalities. Determining how social differences translate into chronic disease remains a challenge, but neuroendocrine pathways appear to play a role."

Monday, October 29, 2007

Silent Minds

I want to point you to an excellent article by Jerome Groopman, with the title of this post, that appeared in a recent New Yorker Magazine. It describes recent work showing that brain imaging of some vegetative patients reveals responses to faces, and other visual and auditory inputs, that are indistinguishable from those of normal subjects (note: there are approximately 35,000 Americans in a vegetative state and another 280,000 in a minimally conscious state). Responses during various mental tasks, such as resolving ambiguous sentences or imagining playing a tennis game, can also be normal. This shows that an assumption held by doctors for decades - that vegetative patients lack capacity for conscious thought - is incorrect. Other vegetative patients (such as Terri Schiavo), in contrast, can show almost no cortical activity.

This all suggests a better medical definition of consciousness is required - such as the ability to report to ourselves or others the content of the representations in our brains, to sustain these representations over time and broadcast them broadly within the brain.

Evolution - with feeling....

A recent issue of American Scientist has a review by Robert Pennock of two books that attempt to show that a mechanistic Darwinian view of the world does not have to lead to a nihilistic ennui, but rather can satisfy our need to feel richness, purpose, and meaning.

With the familiar references to the "uncaring" Darwinian struggle, and the "mechanical" and "pitiless" action of natural selection, evolutionary biology has long been the obvious whipping boy for those who are uncomfortable with scientific naturalism. It is not just fundamentalist religious beliefs that motivate creationists' attacks on evolution; they are also driven by a deep existential angst—a fear that evolution renders the world pointless, emptying it of purpose, meaning and morality.
In "Darwin Loves You:Natural Selection and the Re-enchantment of the World" George Levine argues that evolution
if properly portrayed, is not only perfectly compatible with meaningfulness but provides a new basis for it...He makes the important point that at the same time that evolution pulls the rug out from under anthropocentrism (which is not only a smug but ultimately a dangerous attitude), it provides a foundation for a justifiable form of anthropomorphism. Darwin showed that humans are not the apex of creation but are one with the rest of the biological world, related to all living things through our common ancestors. This discovery allows us to find common ground with other animals without denigrating our humanness, Levine argues, permitting us to legitimately attribute human characteristics (albeit in simpler or incipient forms) to them. This provides an avenue to the re-enchantment of the world, for it shows we are not wrong to find in it a recognizably human notion of meaningfulness. It is wrong to see nature as cold and unfeeling; for those who understand evolutionary processes and relationships, the biological world becomes a warm and caring network of mutual interactions that are suffused with meaning. Levine is a romantic, but not a naive one; he does not close his eyes to those aspects of nature that are "red in tooth and claw," but shows how these need not negate the positive vision.
In "Evolution for Everyone: How Darwin's Theory Can Change the Way We Think about Our Lives" David Sloan Wilson, in the service of finding harmony between evolution and religion:
...discusses some of the evidence for his evolutionary hypothesis that religions are adaptive at the group level, providing practical benefits relating to the specific conditions the group is confronted with...Given the central importance of evolution in biology, the most extraordinary thing about the public's view, Wilson points out, is not that 50 percent don't believe it, but that nearly 100 percent haven't connected it to anything of importance in their lives. One of Wilson's chief goals—one he accomplishes admirably—is to demonstrate the relevance and value of evolutionary biology not just to scientists but to ordinary people. In story after engaging story, he conveys not only the sweep and the power of evolutionary thinking but the grandeur, as Darwin put it, of this view of life. By the end of the book, the reader understands Wilson's metaphor that evolution is an artist that has helped fashion the sculpture that is the living world.

Friday, October 26, 2007

The Outsourced Brain

I can't resist passing on this clever NY Times Op-Ed piece by David Brooks - on the subject of the dissolution of our individual intelligences into the mush of the infosphere.

Different takes on the social brain.

Gobbini et al. show that different types of mentalizing engage different brain regions. The abstract and a summary figure:

We compared two tasks that are widely used in research on mentalizing—false belief stories and animations of rigid geometric shapes that depict social interactions—to investigate whether the neural systems that mediate the representation of others' mental states are consistent across these tasks. Whereas false belief stories activated primarily the anterior paracingulate cortex (APC), the posterior cingulate cortex/precuneus (PCC/PC), and the temporo-parietal junction (TPJ)—components of the distributed neural system for theory of mind (ToM)—the social animations activated an extensive region along nearly the full extent of the superior temporal sulcus, including a locus in the posterior superior temporal sulcus (pSTS), as well as the frontal operculum and inferior parietal lobule (IPL)—components of the distributed neural system for action understanding—and the fusiform gyrus. These results suggest that the representation of covert mental states that may predict behavior and the representation of intentions that are implied by perceived actions involve distinct neural systems. These results show that the TPJ and the pSTS play dissociable roles in mentalizing and are parts of different distributed neural systems. Because the social animations do not depict articulated body movements, these results also highlight that the perception of the kinematics of actions is not necessary to activate the mirror neuron system, suggesting that this system plays a general role in the representation of intentions and goals of actions. Furthermore, these results suggest that the fusiform gyrus plays a general role in the representation of visual stimuli that signify agency, independent of visual form.

Figure - Locations of loci of activations associated with ToM, social animation, and biological motion tasks, projected onto the left and right lateral surfaces of the brain.

Brain changes after rehabilitation of congenital prosopagnosia

Another article on faces...Degutis et al. show MRI changes correlating with a recovery of enhanced amplitude of the N170 ERP (electroencephalogram event related potential)component in response to faces compared to objects after training of a subject with congenital prosopagnosia (face blindness).

We used functional magnetic resonance imaging (fMRI) and electroencephalography (EEG) to measure neural changes associated with training configural processing in congenital prosopagnosia, a condition in which face identification abilities are not properly developed in the absence of brain injury or visual problems. We designed a task that required discriminating faces by their spatial configuration and, after extensive training, prosopagnosic MZ significantly improved at face identification. Event-related potential results revealed that although the N170 was not selective for faces before training, its selectivity after training was normal. fMRI demonstrated increased functional connectivity between ventral occipital temporal face-selective regions (right occipital face area and right fusiform face area) that accompanied improvement in face recognition. Several other regions showed fMRI activity changes with training; the majority of these regions increased connectivity with face-selective regions. Together, the neural mechanisms associated with face recognition improvements involved strengthening early face-selective mechanisms and increased coordination between face-selective and nonselective regions, particularly in the right hemisphere.

Thursday, October 25, 2007

The male chill-out after sex: role for brain oxytocin

Here is an intriguing account from Waldherr and Neumann:

Sexual activity and mating are accompanied by a high level of arousal, whereas anecdotal and experimental evidence demonstrate that sedation and calmness are common phenomena in the postcoital period in humans. These remarkable behavioral consequences of sexual activity contribute to a general feeling of well being, but underlying neurobiological mechanisms are largely unknown. Here, we demonstrate that sexual activity and mating with a receptive female reduce the level of anxiety and increase risk-taking behavior in male rats for several hours. The neuropeptide oxytocin has been shown to exert multiple functions in male and female reproduction, and to play a key role in the regulation of emotionality after its peripheral and central release, respectively. In the present study, we reveal that oxytocin is released within the brain, specifically within the hypothalamic paraventricular nucleus, of male rats during mating with a receptive female. Furthermore, blockade of the activated brain oxytocin system by central administration of an oxytocin receptor antagonist immediately after mating prevents the anxiolytic effect of mating, while having no effect in nonmated males. These findings provide direct evidence for an essential role of an activated brain oxytocin system mediating the anxiolytic effect of mating in males.

It's in the Eyes!

Another curious bit on our brain's specialization for recognizing faces, noting the central role of the eyes. The abstract and a figure:

Unlike most other objects that are processed analytically, faces are processed configurally. This configural processing is reflected early in visual processing following face inversion and contrast reversal, as an increase in the N170 amplitude, a scalp-recorded event-related potential. Here, we show that these face-specific effects are mediated by the eye region. That is, they occurred only when the eyes were present, but not when eyes were removed from the face. The N170 recorded to inverted and negative faces likely reflects the processing of the eyes. We propose a neural model of face processing in which face- and eye-selective neurons situated in the superior temporal sulcus region of the human brain respond differently to the face configuration and to the eyes depending on the face context. This dynamic response modulation accounts for the N170 variations reported in the literature. The eyes may be central to what makes faces so special.

Figure - Simplified neural model of early face processing. Three sources are simultaneously active around 170 msec poststimulus onset. One source in the superior temporal sulcus (STS) region with a radial orientation generates the ERP N170 component. The combination of tangential sources in the fusiform gyrus (FG) and middle occipital gyrus (MOG) generates the MEG M170. The dynamic response modulation of eye- and face-selective neurons within the STS accounts for inversion and CR effects on the face N170 amplitude and for the other existing ERP data on the N170. The + signs represent the amount of activation of the neurons. The absence of + signs signifies that the neurons are not responding.

Wednesday, October 24, 2007

Our visual system is tuned to animals.

New et al. argue that the human attention system evolved category-specific selection criteria to monitor animals (including humans) in the environment. Ohman gives a nice commentary that puts the work in perspective (PDF here) Below is the abstract and a figure from New et.al. (PDF of article here):

Visual attention mechanisms are known to select information to process based on current goals, personal relevance, and lower-level features. Here we present evidence that human visual attention also includes a high-level category-specialized system that monitors animals in an ongoing manner. Exposed to alternations between complex natural scenes and duplicates with a single change (a change-detection paradigm), subjects are substantially faster and more accurate at detecting changes in animals relative to changes in all tested categories of inanimate objects, even vehicles, which they have been trained for years to monitor for sudden life-or-death changes in trajectory. This animate monitoring bias could not be accounted for by differences in lower-level visual characteristics, how interesting the target objects were, experience, or expertise, implicating mechanisms that evolved to direct attention differentially to objects by virtue of their membership in ancestrally important categories, regardless of their current utility.

Sample stimuli with targets circled. Although they are small (measured in pixels), peripheral, and blend into the background, the human (A) and elephant (E) were detected 100% of the time, and the hit rate for the tiny pigeon (B) was 91%. In contrast, average hit rates were 76% for the silo (C) and 67% for the high-contrast mug in the foreground (F), yet both are substantially larger in pixels than the elephant and pigeon. The simple comparison between the elephant and the minivan (D) is equally instructive. They occur in a similar visual background, yet changes to the high-contrast red minivan were detected only 72% of the time (compared with the smaller low-contrast elephant's 100% detection rate).


Brain location of verbal information storage varies between people

A group at Wisconsin has made the interesting observation that group averaged analyses of the sort frequently reported in brain imaging studies may give misleading results if the brain location of the process being studied varies from one individual to the next. Here is their abstract:

What are the precise brain regions supporting the short-term retention of verbal information? A previous functional magnetic resonance imaging (fMRI) study suggested that they may be topographically variable across individuals, occurring, in most, in regions posterior to prefrontal cortex (PFC), and that detection of these regions may be best suited to a single-subject (SS) approach to fMRI analysis. In contrast, other studies using spatially normalized group-averaged (SNGA) analyses have localized storage-related activity to PFC. To evaluate the necessity of the regions identified by these two methods, we applied repetitive transcranial magnetic stimulation (rTMS) to SS- and SNGA-identified regions throughout the retention period of a delayed letter-recognition task. Results indicated that rTMS targeting SS analysis-identified regions of left perisylvian and sensorimotor cortex impaired performance, whereas rTMS targeting the SNGA-identified region of left caudal PFC had no effect on performance. Our results support the view that the short-term retention of verbal information can be supported by regions associated with acoustic, lexical, phonological, and speech-based representation of information. They also suggest that the brain bases of some cognitive functions may be better detected by SS than by SNGA approaches to fMRI data analysis.

Figure: Example from subject 7 of SS and SNGA rTMS targets (orange markers; anterior, SNGA; posterior, SS). White blobs on the brain are load-sensitive regions identified by the SS analysis, which have been merged onto this subject's high-resolution T1-weighted anatomical scan, and are visible at this depth of scalp "peeling."

Reverie

I'm incredulous that over 38,000 people have viewed a recording of Debussy's Reverie that I put on YouTube, and 79 people have made comments (which led me to record a second version). There was also a video response that I thought I would pass on, another video titled "Reverie":

Tuesday, October 23, 2007

Origin of language from cortical motor systems - evidence from fMRI imaging

Meister and Iacoboni offer some interesting observations supporting the idea that language evolved as an exaptation from motor cortical systems. Here is some of their text and a central figure from the paper.

It has been suggested that cortical neural systems for language evolved from motor cortical systems, in particular from those fronto-parietal systems responding also to action observation. While previous studies have shown shared cortical systems for action – or action observation - and language, they did not address the question of whether linguistic processing of visual stimuli occurs only within a subset of fronto-parietal areas responding to action observation. If this is true, the hypothesis that language evolved from fronto-parietal systems matching action execution and action observation would be strongly reinforced

...functional magnetic resonance imaging (fMRI) was used while subjects watched video stimuli of hand-object-interactions and control photo stimuli of the objects and performed linguistic (conceptual and phonological), and perceptual tasks. Since stimuli were identical for linguistic and perceptual tasks, differential activations had to be related to task demands. The results revealed that the linguistic tasks activated left inferior frontal areas that were subsets of a large bilateral fronto-parietal network activated during action perception. Not a single cortical area demonstrated exclusive – or even simply higher - activation for the linguistic tasks compared to the action perception task.

The results show that linguistic tasks do not only share common neural representations but essentially activate a subset of the action observation network if identical stimuli are used. Our findings strongly support the evolutionary hypothesis that fronto-parietal systems matching action execution and observation were co-opted for language, a process known as exaptation.

Figure 3. a) cortical networks activated by the decision task relating to action observation vs rest (Vd-Perc vs rest, red) and action observation vs perceptual decisions on photos of the same objects (Vd-Perc vs Ph-Perc, blue). The large bihemispheric networks found for both contrasts were very similar, suggesting that the fMRI activations found here mainly were related to action observation and not to processes of decision making or object perception required during these tasks, as well. b) Cortical networks activated during the phonological (blue) and the conceptual decision task (red) on photos of manipulable objects. The networks activated by these two linguistic tasks were entirely part of the action observation network depicted in Fig. 3a, in accordance with the hypothesis that development of language out of the mirror neuron system was driven by a process of exaptation.

How potential reward biases our attention

Our eyes dart about (make saccades) rapidly as we view a visual scene - without these small rapid movements we are blind. Milsteen and Doris have made the fascinating observation that how rapidly we make these small movements can be influenced by the potential reward value of the visual target. Here is the work, in abstract-speak:

Basing higher-order decisions on expected value (reward probability x reward magnitude) maximizes an agent's accruement of reward over time. The goal of this study was to determine whether the advanced preparation of simple actions reflected the expected value of the potential outcomes. Human subjects were required to direct a saccadic eye movement to a visual target that was presented either to the left or right of a central fixation point on each trial. Expected value was manipulated by adjusting the probability of presenting each target and their associated magnitude of monetary reward across 15 blocks of trials. We found that saccadic reaction times (SRTs) were negatively correlated to the relative expected value of the targets. Occasionally, an irrelevant visual distractor was presented before the target to probe the spatial allocation of saccadic preparation. Distractor-directed errors (oculomotor captures) varied as a function of the relative expected value of, and the distance of distractors from, the potential valued targets. SRTs and oculomotor captures were better correlated to the relative expected value of actions than to reward probability, reward magnitude, or overall motivation. Together, our results suggest that the level and spatial distribution of competitive dynamic neural fields representing saccadic preparation reflect the relative expected value of the potential actions.

Monday, October 22, 2007

Language Evolution: An invisible hand.

A slightly edited "Editor's Summary" from the Oct. 11 Nature:

As a language evolves, grammatical rules emerge and exceptions die out. Lieberman et al. have calculated the rate at which a language grows more regular, based on 1,200 years of English usage. Of 177 irregular verbs, 79 became regular in the last millennium. And the trend follows a simple rule: a verb's half-life scales as the square root of its frequency. Irregular verbs that are 100 times as rare regularize 10 times faster. The emergence of a rule (such as adding –ed for the past tense) spells death for exceptional forms...In a separate study, Pagel et al. looked at changing word meanings. Across the Indo-European languages, words like 'tail' or 'bird' evolve rapidly and are expressed by many unrelated words. Others, like 'two', are expressed by closely related word forms across the whole language family. Data from over 80 modern languages show that the more a word is used, the less it changes.
And, from Fitch's review of the two papers:

The words of language are not inherited biologically, but are passed on culturally through learning. This process of 'cultural evolution' generates a hierarchical tree of relationships among languages, here illustrated by the Indo-European family. Just as descent with modification in biological evolution (phylogeny) leads to phylogenetic trees, so the analogous process in language change (glossogeny) can lead to glossogenetic trees.
Where should we look to gain a deeper understanding of the invisible hand in the cultural evolution of language? A promising future direction is provided by recent attempts to fuse theoretical models of cultural evolution to experimental investigations of social learning in the laboratory. Experimental investigations of 'iterated learning' — similar to the game of Chinese whispers, where one participant's output serves as input for the next — can provide empirical data to inspire, and constrain, our theories. Sophisticated new theoretical models enable language-learning 'agents' to have both innate biases (in the form of so-called bayesian priors) and powerful statistical learning systems capable of discovering and using environmental regularities. Such models demonstrate the possibility of a very indirect and sometimes non-intuitive relationship between the regularities emerging at the level of a whole population and the underlying generating forces. These forces are individual behaviour and learning (social usage) and innate constraints (in Chomsky's terms, a 'language acquisition device', often called universal grammar).

..some of the most persistent 'cultural replicators' — memes — evolve as slowly as some genes. By documenting and quantifying such effects, this work opens the door to a diverse range of theoretical and empirical investigations. If there is ever to be a science of memetics o rival that of genetics, it should proceed along these lines: combining careful quantitative analysis of well-documented linguistic changes with sophisticated theoretical models capable of taking into account the multilayered complexity of cultural evolution.

Emotional enhancement of memory and learning - a molecular mechanism.

Hu et al. have performed an interesting study of how the rush of noradrenaline during an emotional experience might enhance our ability to recall that experience. It causes a long term enhancement of the activity of nerve synapses using the neurotransmitter glutamate by stimulating the phosphorylation of a particular type of glutamate receptor. I'm afraid the molecular details will only make sense to those of you who know something about the chemistry of nerve transmission, but here they are, as outlined in the article's abstract:

Emotion enhances our ability to form vivid memories of even trivial events. Norepinephrine (NE), a neuromodulator released during emotional arousal, plays a central role in the emotional regulation of memory. However, the underlying molecular mechanism remains elusive. Toward this aim, we have examined the role of NE in contextual memory formation and in the synaptic delivery of GluR1-containing α-amino-3-hydroxy-5-methyl-4-isoxazoleproprionic acid (AMPA)-type glutamate receptors during long-term potentiation (LTP), a candidate synaptic mechanism for learning. We found that NE, as well as emotional stress, induces phosphorylation of GluR1 at sites critical for its synaptic delivery. Phosphorylation at these sites is necessary and sufficient to lower the threshold for GluR1 synaptic incorporation during LTP. In behavioral experiments, NE can lower the threshold for memory formation in wild-type mice but not in mice carrying mutations in the GluR1 phosphorylation sites. Our results indicate that NE-driven phosphorylation of GluR1 facilitates the synaptic delivery of GluR1-containing AMPARs, lowering the threshold for LTP, thereby providing a molecular mechanism for how emotion enhances learning and memory.

Saturday, October 20, 2007

A Wisconsin fall...

My partner and I went driving and walking in the Wisconsin countryside yesterday afternoon - here is an apple orchard, and the ice age trail.

The well-tempered web

I wanted to pass on this link to an engaging article by New Yorker music critic Alex Ross, on his experience with classical music culture on the web. The Internet may be killing the pop CD, but it's helping classical music. The article contains very useful links to many music sites.

Friday, October 19, 2007

Pogue’s Imponderables

Questions that N.Y. Times technical writer David Pogue doesn't have answers to. If you know the answers, fill him in at nytimes.com/pogue.

* Why is Wi-Fi free at cheap hotels, but $14 a night at expensive ones?

* What happens to software programs when their publishers go out of business?

* Would the record companies sell more music online if it weren't copy-protected?

* Do cellphones cause brain cancer?

* What's the real reason you have to turn off your laptop for takeoff?

* Why can't a digital S.L.R. camera record video?

* Wi-Fi on airplanes. What's taking so long?

* Who are the morons who respond to junk-mail offers, thereby keeping spammers in business?

* I'm told that they could make a shirt-pocket digital camera that takes pictures like an S.L.R., but it would cost a lot. So why don't they make one for people who can afford it?

* How come there are still no viruses for Mac OS X? If it has 6 percent of the market, shouldn't it have 6 percent of the viruses?

* Do shareware programmers pay taxes on all those $20 contributions?

* How are we going to preserve all of our digital photos and videos for future generations?

* Why are there no federal rebates or tax credits for solar power?

* Why do you have to take tape camcorders out of your carry-on at airport security, but not the tapeless kind? Couldn't you hide a bomb equally well in either one? (Actually, I have about 500 more logic questions about the rules at airport security, but I have a feeling they'll remain answerless for a very long time.)

* Laptops, cameras and cellphones have improved by a thousand percent in the last ten years. Why not their batteries?

* SmartDisplay, Spot Watch, U.M.P.C., Zune… when will Microsoft realize that it's not a hardware company?

* Why don't public sinks have foot pedals?

* Why don't all hotels have check-in kiosks like airlines do?

* Five billion dollars a year spent on ringtones? What the?

* How come cellphone signal-strength bars are so often wrong?

* Do P.R. people really expect anyone to believe that the standard, stilted, second-paragraph C.E.O. quote was really uttered by a human being?

* Why aren't there recycling bins for bottles and cans where they're most obviously needed, like food courts and cafeterias?

* Why doesn't someone start a cellphone company that bills you only for what you use? That model works O.K. for the electricity, gas and water companies —and people would beat a path to its door.

* Why doesn't everyone have lights that turn off automatically when the room is empty?

* What's the deal with Palm?

* Why are so many people rude on the Internet?

If you know the answers, by all means—fill us in at nytimes.com/pogue.

Genetic dissociation of multiple dopamine roles in learning

Here is the abstract of Frank et al., who show that three genetic variants of the dopamine systems that influence our reactions to positive and negative outcomes (and anticipations) have different effects on human reinforcement learning.

What are the genetic and neural components that support adaptive learning from positive and negative outcomes? Here, we show with genetic analyses that three independent dopaminergic mechanisms contribute to reward and avoidance learning in humans. A polymorphism in the DARPP-32 gene, associated with striatal dopamine function, predicted relatively better probabilistic reward learning. Conversely, the C957T polymorphism of the DRD2 gene, associated with striatal D2 receptor function, predicted the degree to which participants learned to avoid choices that had been probabilistically associated with negative outcomes. The Val/Met polymorphism of the COMT gene, associated with prefrontal cortical dopamine function, predicted participants' ability to rapidly adapt behavior on a trial-to-trial basis. These findings support a neurocomputational dissociation between striatal and prefrontal dopaminergic mechanisms in reinforcement learning. Computational maximum likelihood analyses reveal independent gene effects on three reinforcement learning parameters that can explain the observed dissociations.

A Memory Toolbox

A reader sends this link to 75 tips for going from amnesic to elephantic...

Parallel Distributed Processing and Semantic Cognition

Timothy T. Rogers and James L. McClelland have distilled the essence of the arguments in their book "Semantic Cognition: A Parallel Distributed Processing Approach" for an article (PDF here) to appear in Brain and Behavioral Sciences with peer commentary. Here is their abstract:

In our recent book, we present a parallel distributed processing theory of the acquisition, representation and use of human semantic knowledge. The theory proposes that semantic abilities arise from the flow of activation amongst simple, neuron-like processing units, as governed by the strengths of interconnecting weights; and that acquisition of new semantic information involves the gradual adjustment of weights in the system in response to experience. These simple ideas explain a wide range of empirical phenomena from studies of categorization, lexical acquisition, and disordered semantic cognition. In this précis we focus on phenomena central to the reaction against similarity-based theories that arose in the 1980's and that subsequently motivated the "theory-theory" approach to semantic knowledge. Specifically, we consider i) how concepts differentiate in early development, ii) why some groupings of items seem to form "good" or coherent categories while others do not, iii) why different properties seem central or important to different concepts, iv) why children and adults sometimes attest to beliefs that seem to contradict their direct experience, v) how concepts reorganize between the ages of 4 and 10, and vi) the relationship between causal knowledge and semantic knowledge. The explanations for these phenomena are illustrated with reference to a simple feed-forward connectionist model; and the relationship between this simple model, the broader theory, and more general issues in cognitive science are discussed.

Thursday, October 18, 2007

In an Ultimatum Game, Chimps, but not humans, are rational maximizers

Another interesting bit of work from Tomasello's group (PDF here), in which they devised an ingenious apparatus for a mini-ultimatum game, a reduced form of the ultimatum game in which proposers are given a choice between making one of two pre-set offers which the responder can then accept or reject. The proposer had as one option an amount that would typically be rejected by a human responder as unfair, namely 80% for the proposer and 20% for the responder. The most important finding was that responders tended to accept any offer. These results support the hypothesis that other-regarding preferences and aversion to inequitable outcomes, which play key roles in human social organization, distinguish us from our closest living relatives. Here is their abstract, slightly edited:

Traditional models of economic decision-making assume that people are self-interested rational maximizers. Empirical research has demonstrated, however, that people will take into account the interests of others and are sensitive to norms of cooperation and fairness. In one of the most robust tests of this finding, the ultimatum game, individuals will reject a proposed division of a monetary windfall, at a cost to themselves, if they perceive it as unfair. Here we show that in an ultimatum game, humans' closest living relatives, chimpanzees (Pan troglodytes), are rational maximizers and are not sensitive to fairness.

Figure: Illustration of the testing environment. The proposer, who makes the first choice, sits to the responder's left. The apparatus, which has two sliding trays connected by a single rope, is outside of the cages. (A) By first sliding a Plexiglas panel (not shown) to access one rope end and by then pulling it, the proposer draws one of the baited trays halfway toward the two subjects. (B) The responder can then pull the attached rod, now within reach, to bring the proposed food tray to the cage mesh so that (C) both subjects can eat from their respective food dishes (clearly separated by a translucent divider).

Interactions between Declarative and Procedural Memories

Brown and Robertson do a simple experiment showing interaction between two main memory systems usually thought to be independent. Their abstract, slightly edited:

The acquisition of declarative (i.e., facts) and procedural (i.e., skills) memories may be supported by independent systems. This same organization may exist, after memory acquisition, when memories are processed off-line during consolidation. Alternatively, memory consolidation may be supported by interactive systems. This latter interactive organization predicts interference between declarative and procedural memories. Here, we show that procedural consolidation, expressed as an off-line motor skill improvement, can be blocked by declarative learning over wake, but not over a night of sleep. [note: the procedural task was learning a sequence of visually cued button presses at four possible postions.] The extent of the blockade on procedural consolidation was correlated to participants' declarative word recall. Similarly, in another experiment, the reciprocal relationship was found: declarative consolidation was blocked by procedural learning over wake, but not over a night of sleep. [note: The declarative task was learning a list of 16 words each individually presented on a computer screen for two seconds, with the list being presented in the same order five times.] The decrease in declarative recall was correlated to participants' procedural learning. These results challenge the concept of fixed independent memory systems; instead, they suggest a dynamic relationship, modulated by when consolidation takes place, allowing at times for a reciprocal interaction between memory systems.

Wednesday, October 17, 2007

Facts are no match for gossip...

In yesterday's Science NY Times, John Tierny describes work by Ralf D. Sommerfeld and colleagues on human reciprocity that has a surprising result (PDF here). Here are some clips:

Language, according to the anthropologist Robin Dunbar, evolved because gossip is a more efficient version of the “social grooming” essential for animals to live in groups...Gossip also told people whom to trust, and the prospect of a bad reputation discouraged them from acting selfishly, so large groups could peacefully cooperate. At least, that was the theory: gossip promoted the “indirect reciprocity” that made human society possible.

To test it, researchers at the Max Planck Institute for Evolutionary Biology and the University of Vienna gave 10 Euros apiece to 126 students and had them play a game that put them in a dilemma. On each turn, the players would be paired off, and one of them was offered a chance to give 1.25 Euros to the other. If he agreed, the researchers added a bonus of .75 Euro so that the recipient ended up gaining 2 Euros...If the first player refused to give the money, he’d save 1.25 Euros, but if others found out about his miserliness they might later withhold money from him. As the game progressed, with the players changing partners frequently and alternating between the donor and recipient roles, the players were given information about their partners’ past decisions...Sometimes the donor was shown a record of what the partner had done previously while playing the donor role. The more generous this partner had earlier been toward other players, the more likely the donor was to give him something...Sometimes the donor was shown gossip about the partner from another player. When the partner was paid a compliment like “spendabler spieler!” — generous player! — the donor was more likely to give money. But the donor turned stingy when he saw gossip like “übler geizkragen” — nasty miser.

So far, so good. As predicted, gossip promoted indirect reciprocity. The research, published in the Proceedings of the National Academy of Sciences [Note, I haven't found this article yet in a PNAS search], showed that most people passed on accurate gossip and used it for the common good. They rewarded cooperative behavior even when they themselves weren’t directly affected by the behavior...If a cooperation game like this was played without consequences for the players’ reputations — as has been done in other experiments — most players would be miserly, and cooperation would collapse. In this experiment they were generous most of the time, and on average ended up with twice as much money as they had at the beginning of the game.

But here’s the disconcerting news from the experiment. In a couple of rounds, each donor was given both hard facts and gossip. He was given a record of how his partner had behaved previously as well as some gossip — positive gossip in one round, negative in another...The donor was told that the source of the gossip didn’t have any extra information beyond what the donor could already see for himself. Yet the gossip, whether positive or negative, still had a big influence on the donors’ decisions, and it didn’t even matter if the source of the gossip had a good reputation himself. On average, cooperation increased by about 20 percent if the gossip was good, and fell by 20 percent if the gossip was negative.
Why is this?
It could be,” Sommerfeld suggested, “that we are just more adapted to listen to other information than to observe people, because most of the time we’re not able to observe how other people are behaving. Thus we might believe we have missed something."

Most popular consciousness papers for September 2007

From the ASSC Eprints Archive:

1. Rosenthal, David (2007) Consciousness and its function. In: 11th annual
meeting of the Association for the Scientific Study of Consciousness, 22-25
June 2007, Las Vegas, USA. 1014 downloads from 20 countries.
http://eprints.assc.caltech.edu/293/
2. Koriat, A. (2006) Metacognition and Consciousness. In: Cambridge handbook
of consciousness. Cambridge University Press, New York, USA. 870 downloads
from 18 countries. http://eprints.assc.caltech.edu/175/
3. Windt, Jennifer Michelle and Metzinger, Thomas (2006) The philosophy of
dreaming and self-consciousness: What happens to the experiential subject
during the dream state? In: The new science of dreaming. 834 downloads from
16 countries. http://eprints.assc.caltech.edu/200/
4. Sagiv, Noam and Ward, Jamie (2006) Crossmodal interactions: lessons from
synesthesia. In: Visual Perception, Part 2. Progress in Brain Research,
Volume 155. 814 downloads from 14 countries.
http://eprints.assc.caltech.edu/224/
5. Droege, Paula (2007) ASSC-11 Conference Report. In: 11th annual meeting
of the Association for the Scientific Study of Consciousness, June 22-25,
2007, Las Vegas, Nevada. 798 downloads from 18 countries.
http://eprints.assc.caltech.edu/323/

Motivation alters physical perception

Here is a clip from the Editor's choice section of the Oct. 5 issue of Science:

Students in elementary physics classes are introduced to the concept of frame of reference--the spatial coordinate system used by an observer to describe events--for instance, in the context of the perceived motion of trees by a passenger in a moving automobile. Adding in the dimension of time leads into non-intuitive territory, as in the example of a traveling astronaut who returns to Earth younger than her stay-at-home twin.

Building on previous work that demonstrated that internal physiological states can influence one's perception of physical quantities (such as thirsty people being more likely to characterize objects as transparent; that is, resembling water), Balcetis and Dunning show that internal psychological states are also capable of altering our perception of the external world. They induced states of high or low cognitive dissonance (a mismatch between thought and action) by asking or telling two groups of students to walk across campus wearing various fruit- and vegetable-themed adornments. In order to render a freely chosen yet somewhat embarrassing task less unpleasant to fulfill, the first set of students mentally shortened the distance they had to cover by estimating it to be fully 40% less than the average estimate made by the second group. Intriguingly, the route to ameliorating the state of dissonance appeared to be purely perceptual, as the free-choice students did not shorten their time of exposure by walking faster; in fact, they took about 10% longer.
The abstract of the original article;
Two studies demonstrated that the motivation to resolve cognitive dissonance affects the visual perception of physical environments. In Study 1, subjects crossed a campus quadrangle wearing a costume reminiscent of Carmen Miranda. In Study 2, subjects pushed themselves up a hill while kneeling on a skateboard. Subjects performed either task under a high-choice, low-choice, or control condition. Subjects in the high-choice conditions, presumably to resolve dissonance, perceived the environment to be less aversive than did subjects in the low-choice and control conditions, seeing a shorter distance to travel (Study 1) and a shallower slope to climb (Study 2). These studies suggest that the impact of motivational states extends from social judgment down into perceptual processes.

Tuesday, October 16, 2007

Baboon Metaphysics

Nicholas Wade comments (PDF here) on the work of Cheney and Seyfarth, whose most recent book has the title of this post. They have carried out an ingenious series of experiments in the wild to probe how the baboon's mind keeps track of transient relationships:

Royal is a cantankerous old male baboon whose troop of some 80 members lives in the Moremi Game Reserve in Botswana. A perplexing event is about to disturb his day....From the bushes to his right, he hears a staccato whoop, the distinctive call that female baboons always make after mating. He recognizes the voice as that of Jackalberry, the current consort of Cassius, a male who outranks Royal in the strict hierarchy of male baboons. No hope of sex today....But then, surprisingly, he hears Cassius’s signature greeting grunt to his left. His puzzlement is plain on the video made of his reaction. You can almost see the wheels turn slowly in his head:...“Jackalberry here, but Cassius over there. Hmm, Jackalberry must be hooking up with some one else. But that means Cassius has left her unguarded. Say what — this is my big chance!”...The video shows him loping off in the direction of Jackalberry’s whoop. But all that he will find is the loudspeaker from which researchers have played Jackalberry’s recorded call.
Although Baboons excel at the skills required for maintaining social networks regulated by matrilineal lines and dominance hierarchies, there is no evidence that they attribute beliefs or ideas to other animals, or that 'they know that they know.' They provide an example of what sort of social and cognitive complexity is possible in the absence of language and a theory of mind.

The prospective brain

I've been meaning to point you to a nice review article by Daniel Schacter and colleagues (PDF here). Here is the abstract and a summary figure.

A rapidly growing number of recent studies show that imagining the future depends on much of the same neural machinery that is needed for remembering the past. These findings have led to the concept of the prospective brain; an idea that a crucial function of the brain is to use stored information to imagine, simulate and predict possible future events. We suggest that processes such as memory can be productively re-conceptualized in light of this idea.

The core brain system that is consistently activated while remembering the past, envisioning the future and during related forms of mental simulation is illustrated schematically. Prominent components of this network include medial prefrontal regions, posterior regions in the medial and lateral parietal cortex (extending into the precuneus and the retrosplenial cortex), the lateral temporal cortex and the medial temporal lobe. Moreover, regions within this core brain system are functionally correlated with each other and, prominently, with the hippocampal formation. We suggest that this core brain system functions adaptively to integrate information about relationships and associations from past experiences, in order to construct mental simulations about possible future events.

Monday, October 15, 2007

New phases of our lives...

NY Times columnist David Brooks muses on how the phases of our life have increased in number (PDF here). Some clips:

There used to be four common life phases: childhood, adolescence, adulthood and old age. Now, there are at least six: childhood, adolescence, odyssey, adulthood, active retirement and old age. Of the new ones, the least understood is odyssey, the decade of wandering that frequently occurs between adolescence and adulthood...People who were born before 1964 tend to define adulthood by certain accomplishments — moving away from home, becoming financially independent, getting married and starting a family....In 1960, roughly 70 percent of 30-year-olds had achieved these things. By 2000, fewer than 40 percent of 30-year-olds had done the same.

...you can see the spirit of fluidity that now characterizes this stage....everything seems to give way to a less permanent version of itself...Dating gives way to Facebook and hooking up. Marriage gives way to cohabitation....Graduating seniors don’t find corporations offering them jobs that will guide them all the way to retirement. Instead they find a vast menu of information economy options...what we’re seeing is the creation of a new life phase, just as adolescence came into being a century ago...European nations are traveling this route ahead of us... Europeans delay marriage even longer than we do and spend even more years shifting between the job market and higher education...Someday people will look back and wonder at the vast social changes wrought by the emerging social group that saw their situations first captured by “Friends” and later by “Knocked Up.”

How to get health facts completely wrong....

John Tierney reviews Gary Taubes account (in "“Good Calories, Bad Calories”; Knopf, 2007) of how the health science establishment got it completely wrong, from the basic science on through official government pronouncements on dietary fat and hearth disease (PDF here). Some clips:

The notion that fatty foods shorten your life began as a hypothesis based on dubious assumptions and data; when scientists tried to confirm it they failed repeatedly.
Even so, in 1988, the surgeon general, C. Everett Koop, proclaimed ice cream to a be public-health menace right up there with cigarettes.This happened because of what social scientists call a cascade:
We like to think that people improve their judgment by putting their minds together, and sometimes they do. The studio audience at “Who Wants to Be a Millionaire” usually votes for the right answer. But suppose, instead of the audience members voting silently in unison, they voted out loud one after another. And suppose the first person gets it wrong...If the second person isn’t sure of the answer, he’s liable to go along with the first person’s guess. By then, even if the third person suspects another answer is right, she’s more liable to go along just because she assumes the first two together know more than she does. Thus begins an “informational cascade” as one person after another assumes that the rest can’t all be wrong...Because of this effect, groups are surprisingly prone to reach mistaken conclusions even when most of the people started out knowing better... If, say, 60 percent of a group’s members have been given information pointing them to the right answer (while the rest have information pointing to the wrong answer), there is still about a one-in-three chance that the group will cascade to a mistaken consensus.

Friday, October 12, 2007

Your Money and Your Brain

I thought I would pass on this brief commentary by Joe Nocera in the NY Times (PDF here), which emphasizes comments by Jason Zweig on how our emotional brains are not very well suited for making rational financial decisions.

A neural marker of consciousness

Here is the author's summary of an interesting article by Del Cul et al. in PlosBiology.

Understanding the neural mechanisms that distinguish between conscious and nonconscious processes is a crucial issue in cognitive neuroscience. In this study, we focused on the transition that causes a visual stimulus to cross the threshold to consciousness, i.e., visibility. We used a backward masking paradigm in which the visibility of a briefly presented stimulus (the “target”) is reduced by a second stimulus (the “mask”) presented shortly after this first stimulus. (Human participants report the visibility of the target.) When the delay between target and mask stimuli exceeds a threshold value, the masked stimulus becomes visible. Below this threshold, it remains nonvisible. During the task, we recorded electric brain activity from the scalp and reconstructed the cortical sources corresponding to this activity. Conscious perception of masked stimuli corresponded to activity in a broadly distributed fronto-parieto-temporal network, occurring from about 300 ms after stimulus presentation. We conclude that this late stage, which could be clearly separated from earlier neural events associated with subliminal processing and mask-target interactions, can be regarded as a marker of consciousness.


Figure: Top, depth of cortical processing: subliminal stimuli (left panel) should evoke a strong activation in extrastriate visual cortex, but their intensity should quickly decrease in higher visual areas; only conscious stimuli (right panel) should trigger a late surge of activation in a global prefronto-parietal network. Bottom, schematic time course of activation as a function of masking strength. Masking is expected to have little effect on early visual activation but to modulate the strength of activation in higher visual areas. Furthermore, there should be a nonlinear effect of masking strength in prefrontal cortex, with a similar late top-down activation peak occurring simultaneously in visual areas

Where the brain decides how much we are willing to pay.

Plassmann et al. show some brain correlates of our willingness to pay:

An essential component of every economic transaction is a willingness-to-pay (WTP) computation in which buyers calculate the maximum amount of financial resources that they are willing to give up in exchange for the object being sold. Despite its pervasiveness, little is known about how the brain makes this computation. We investigated the neural basis of the WTP computation by scanning hungry subjects' brains using functional magnetic resonance imaging while they placed real bids for the right to eat different foods. We found that activity in the medial orbitofrontal cortex and in the dorsolateral prefrontal cortex encodes subjects' WTP for the items. Our results support the hypothesis that the medial orbitofrontal cortex encodes the value of goals in decision making.
Neural correlates of WTP. A, B, Activity in the medial OFC and the DLPFC was positively correlated with WTP at the time of evaluation in the free trials more than in the forced trials.

Thursday, October 11, 2007

What the F***?

An article by Steven Pinker on cursing.

Google's evil eye....

...thought I would link you to this interesting article.

Radiohead - the modern troubadours?

An article in the Arts section of today's NY Times temporarily stirred me out of my curmudgeonly old fart persona. Just as a federal jury in Minnesota last week decided that a mother found liable for copyright infringement for sharing music online should pay damages amounting to about $9,250 apiece for 24 songs, the British Rock group Radiohead has made their latest album "In Rainbows" available for download, letting their fans decide how much they want to pay for it. This has brought a new climax in the pricing pandemonium in the on-line music industry summed up by Radiohead manager Bryce Edge:

Digital technology has reintroduced the age of the troubadour. You are worth what people are prepared to give you in the digital age because they can get it for nothing.
In another departure from convention:
...the band declined to send out early copies of the music for reviewers and has not settled on a traditional single to push to radio stations. As a result, programmers are improvising. In San Francisco, for instance, the rock station KITS-FM, Live 105, has the entire album on its Web site (live105.com) and will let fans vote to determine which songs merit airplay.

I just checked out this site, and proceeded to buy and download the new album.

See-through frog...

Just the thing for a budding young scientist's holiday stocking...From the Oct. 3 issue of Nature Magazine:

Japanese biologists have created what they call the world's first see-through creature with four legs. (Some fish are naturally transparent.) The frogs started out as ordinary Japanese brown frogs (Rana japonica ), but crossing animals with recessive genes for light-coloured skin led to transparency. Internal organs, eggs and other normally concealed innards are all on full display in the new amphibian (pictured). Its creator, Masayuki Sumida of Hiroshima University, plans to seek a patent, according to the AFP news agency.

How we see over 10,000-fold changes in light intensity

The first 35 years of my professional life were spent studying the excitation and adaptation of photoreceptor cells. This motivates me to point out a beautiful piece of work by Dunn et al. showing how different circuits in the retina collaborate to let us see over an amazingly wide range of environmental light intensities. Here is their abstract, and figures from the paper showing the cells involved:

We see over an enormous range of mean light levels, greater than the range of output signals retinal neurons can produce. Even highlights and shadows within a single visual scene can differ approximately 10,000-fold in intensity—exceeding the range of distinct neural signals by a factor of approximately 100. The effectiveness of daylight vision under these conditions relies on at least two retinal mechanisms that adjust sensitivity in the approximately 200 ms intervals between saccades. One mechanism is in the cone photoreceptors (receptor adaptation)and the other is at a previously unknown location within the retinal circuitry that benefits from convergence of signals from multiple cones (post-receptor adaptation). Here we find that post-receptor adaptation occurs as signals are relayed from cone bipolar cells to ganglion cells. Furthermore, we find that the two adaptive mechanisms are essentially mutually exclusive: as light levels increase the main site of adaptation switches from the circuitry to the cones. These findings help explain how human cone vision encodes everyday scenes, and, more generally, how sensory systems handle the challenges posed by a diverse physical environment.

Figure 1: Midget and parasol ganglion cells adapt at lower backgrounds than L cones. Schematic of primate midget and parasol pathways with fluorescent images of cones in slice and ganglion cells in flat mount.

Figure 2: Post-receptor adaptation occurs in signal transfer from cone bipolar cells to ganglion cells. The figure shows fluorescent images of a midget cone bipolar cell (left panel) and a diffuse cone bipolar cell (right panel) in slice. OPL, outer plexiform layer; INL, inner nuclear layer; IPL, inner plexiform layer.

The wireless epidemic

Jon Kleinberg, best known for his work on web searching that paved the way for Google and the rest, writes on the threat posed by computer viruses and worms in our increasingly 'wireless' age, concluding that biological models of virus transmission are increasingly relevant for assessing the emerging threat. Here are a few clips:

Traditionally, computer viruses have propagated on networks that bear little resemblance to the networks of physical contact through which their biological counterparts spread. But a growing body of research shows that the increasing use of short-range wireless communication networks might cause the two models to converge....Diseases in plant populations, or animal diseases such as rabies, are heavily constrained by geographical proximity and the relatively fixed physical locations of the infected individuals. Models of these diseases have been extended using detailed data on patterns of travel within cities and by air worldwide in attempts to analyse disease outbreaks in human populations...Epidemics on the Internet are even more diverse. At the most general level, there is a distinction between computer viruses, which 'piggyback' on data exchanged between users, and computer worms, which more actively direct their own transmission through a network...

Very roughly.. one could view models of biological epidemics as rooted in spatial networks, and expanding into less spatial realms to model the technologies that have accelerated human travel. Meanwhile, research on cyber-epidemics has occupied the non-spatial end of the spectrum, with its diverse and far-flung connections, when modelling global communication technologies such as the Internet.

..the spread of short-range wireless communication technologies such as Bluetooth, and the emergence of worms that exploit these systems is disrupting this dichotomy by making possible computer-virus outbreaks whose progress closely tracks human mobility patterns. These types of wireless worm are designed to infect mobile devices such as cell phones, and then to continuously scan for other devices within a few tens of metres or less, looking for new targets. A computer virus thus becomes something you catch not necessarily from a compromised computer halfway around the world, but possibly from the person sitting next to you on a bus, or at a nearby table in a restaurant.

In assessing the risks of such attacks, and developing countermeasures against them, it is intriguing to contemplate how we might draw on expertise from the field of human epidemiology in understanding how contagion spreads...Analogies to biological epidemics can also be exploited for beneficial purposes, in the design of computer-network protocols. For mobile devices, epidemiology helps in dealing with the problem of intermittent connectivity: that the routing of traffic must conform to a dynamic and unpredictable network structure as the owners of mobile devices move around. The result is a growing interest in opportunistic routing, in which messages are passed between devices that come into physical proximity, with the goal of eventually reaching a specified recipient. The development of such protocols has drawn on detailed data concerning human mobility and contact patterns.

Wednesday, October 10, 2007

An acetylcholine receptor agonist improves cognition

The alpha-7 nicotinic acetylcholine receptor (nAChR) plays an important role in cognitive processes and may represent a drug target for treating cognitive deficits in neurodegenerative and psychiatric disorders. Bitner et al. study the effects of a particular AChR enhancer, or agonist, whose simple name is A-582941.

The figure shows the general structure of this class of molecules. A-582941 enhanced cognitive performance in behavioral assays including the monkey delayed matching-to-sample, rat social recognition, and mouse inhibitory avoidance models that capture domains of working memory, short-term recognition memory, and long-term memory consolidation, respectively. Their results demonstrate that alpha-7 nAChR agonism can lead to broad-spectrum efficacy in animal models at doses that enhance ERK1/2 (extracellular-signal regulated kinase) and CREB (cAMP response element-binding protein) phosphorylation/activation and may represent a mechanism that offers potential to improve cognitive deficits associated with neurodegenerative and psychiatric diseases, such as Alzheimer's disease and schizophrenia.

Most Viewed MindBlog posts...

I occasionally check Feedburner.com to observe web traffic to this blog, and pulled up the following list of most viewed posts. The left column indicates the number of views and the right indicates clicks on links in the post. Entering a few words of the title in the "Search MindBlog" box gets you to a given post...

Non-materialist neuroscience

Here is an discussion on what the authors call the latest installment of the war on science. From their introduction:

Non-materialist neuroscience is the latest front in the war on science. The battle has been a long time coming and it is surprising it has taken so long to get going. Modern neuroscience is rapidly reducing much of human thought, emotion and behavior into component pieces of neuronal interactions. The combination of computational modeling and non-invasive imaging of living brains has allowed researchers to begin describing how complex thought emerges from the firing patterns of neurons. In a way neuroscience is the death knell of dualism. When materialist causes become both necessary and sufficient to explain all of human thought then parsimony dictates that references to a soul or other supernatural entities can be tossed out.

Non-materialist neuroscience is a reaction to these discoveries, a rallying cry for dualism. Like creationism and intelligent design this "new" neuroscience is a reactionary movement against science. Rather than a hypothesis that leads to predictions and experiments, it is simply a catalog of things modern neuroscience supposedly cannot yet explain.

Unsurprisingly, the movement is spear-headed by intelligent design lackeys from the Discovery Institute and related affiliates. The primary proponents of the movement are Michael Egnor, a neurosurgeon and recent contributor to the Discovery Institute blog, Denyse O'Leary a Canadian "journalist" who runs her own blog dedicated to non-materialist neuroscience and likes to copy and paste these entries over on William Dembski's blog as well, and Mario Beauregard the author with O'Leary of a recent book on the subject of non-materialist neuroscience The Spiritual Brain: A Neuroscientist's Case for the Existence of the Soul.

Tuesday, October 09, 2007

Musicians have enhanced subcortical processing

Musical training is known to modify cortical organization. Musacchia et al. show that:

...such modifications extend to subcortical sensory structures and generalize to processing of speech. Musicians had earlier and larger brainstem responses than nonmusician controls to both speech and music stimuli presented in auditory and audiovisual conditions, evident as early as 10 ms after acoustic onset. Phase-locking to stimulus periodicity, which likely underlies perception of pitch, was enhanced in musicians and strongly correlated with length of musical practice. In addition, viewing videos of speech (lip-reading) and music (instrument being played) enhanced temporal and frequency encoding in the auditory brainstem, particularly in musicians. These findings demonstrate practice-related changes in the early sensory encoding of auditory and audiovisual information.

Do you need more hassles?

Try out this.

Some rambling on "Selves" and "Purpose"

The recent posts on Alwyn Scott and the Blakesless' book prompt me to this random walk....

Self conscious "Purpose" of the sort we humans experience, in the service of crafting new political movements or environments, is an evolved psychology that (sometimes) helps pass on our genes, and requires our distinctively human self reflective "I". Our behavior and that of other animals also reflects a kind of purpose that has been formed by our evolutionary and developmental history. In other animals such behaviors are acted out on the cusp of an eternal present - there is no evidence that they "know that they know" in the way that we can.

Both modern neuroscience (cf. the quote from the Blakesless' book) and Buddhist psychology inform us that the self and the purpose that each of us experiences is an illusion or confabulation of our brains - hopefully a useful one - whose utility is tested by how it enhances our energy and individual survival. This 'illusion' is a powerful instrument of downward causation, regulating our psychological, immune, neuro-endocrine robustness.

What is especially amazing is that our human body/brain can sometimes use meditative or other techniques to bootstrap to a level of metacognition that rests antecedent to - and can be the detached observer of - the generation of this illusion of a self and its purposes.

The maximum power of our self illusion, for most of us, goes with our heartfelt immersion and belief in it (i.e., our delusion). From such a immersion, it can be more difficult to discern or appreciate the different selves and purposes of other humans, and their cultures and historical eras.

Monday, October 08, 2007

Rich and Poor

San Paulo, Brazil.

Playing Action Video Games Reduces Gender Differences in Spatial Cognition

From Feng, Spence, and Pratt (PDF here):

We demonstrate a previously unknown gender difference in the distribution of spatial attention, a basic capacity that supports higher-level spatial cognition. More remarkably, we found that playing an action video game can virtually eliminate this gender difference in spatial attention and simultaneously decrease the gender disparity in mental rotation ability, a higher-level process in spatial cognition. After only 10 hr of training with an action video game, subjects realized substantial gains in both spatial attention and mental rotation, with women benefiting more than men. Control subjects who played a non-action game showed no improvement. Given that superior spatial skills are important in the mathematical and engineering sciences, these findings have practical implications for attracting men and women to these fields.
From their article:
The experimental group was trained using Medal of Honor: Pacific Assault, which was chosen because it is similar to the games typically played by players in Experiment 1 [note: which compared students based on their self reports of game use] and because it has been used before in attention training studies. This game is a 3-D first-person shooter game that requires intense visual monitoring and attentional resources. The control group played Ballance, a 3-D puzzle game that involves steering a ball through a hovering maze of paths and rails with obstacles such as seesaws, suspension bridges, and pendulums.

Plasticity and learning in the human mirror neuron system

I pass on a review by Welberg of an interesting study by Catmur et al. [Catmur, C., Walsh, V. & Heyes, C. Sensorimotor learning configures the human mirror system. Curr. Biol. 17, 1527–1531 (2007)]:

Neurons in the frontoparietal mirror system fire when one performs an action and when one observes someone else performing that same action. This system is thought to have a role in social cognition and, perhaps, in language acquisition. How the mirror neurons map sensory input onto its motor representation is unknown, but Catmur et al. demonstrate that these representations are not innate and can be altered by training.

The authors used transcranial magnetic stimulation (TMS) to stimulate the motor cortex of volunteers who were watching a video of a hand. When the volunteers watched the hand's index finger move, the TMS-induced motor-evoked potential (MEP) was greater in the abductor muscle of their own index finger than when they watched the little finger move; conversely, the MEP of their little finger's abductor muscle was greatest when they watched the little finger move. In other words, a muscle showed MEP enhancement when its owner watched a movement that is normally performed by that muscle; this 'mirror effect' is thought to reflect activity of the mirror neuron system.

Half of the volunteers then underwent incongruent training trials, in which they were asked to extend their little finger if the video showed a hand extending the index finger, and vice versa. People in congruent trials simply had to repeat the movement they saw in the video. The incongruent trials were assumed to train the mirror system to associate an observed finger movement with movement of a different finger of the volunteer's own hand.

Measuring TMS-induced MEPs after training, the authors found that volunteers who had undergone the incongruent training now showed greater MEPs in the muscle of one finger when watching the 'wrong' finger move in the video, indicating that a reversal of muscle-specific MEP enhancement during action observation had taken place.

This study shows that the 'mirror properties' of the mirror system are not innate. Rather, they can be trained, through sensorimotor experience, to transform observation into action. These findings imply that insufficient social interaction and consequent inadequate sensory experience might affect the development of the mirror neuron system, for example, in children with autism.

Friday, October 05, 2007

New research on ageing

Nature Magazine offers a special open access supplement with several excellent articles on recent research on ageing. Also, they offer to send a free print copy.

Striking Images....

Here are the first place winners of Science Magazine's 2007 Visualization Challenge, in which editors evaluate submissions that try to bring scientific data to life through images, illustrations, computer graphics, and animations. In the first, 182 thin CT "slices" are stacked together to create a 3D image looking upward at the sinuses from underneath the head. In the second, Irish ocean moss is spread out for photography.

How Meaning Shapes Seeing

This is the title of an interesting article by Koivisto and Revonsuo in Psychological Science. They show that semantic meaning influences inattentional blindness. Here is their abstract:

Inattentional blindness refers to the failure to see an unexpected object that one may be looking at directly when one's attention is elsewhere. We studied whether a stimulus whose meaning is relevant to the attentional goals of the observer will capture attention and escape inattentional blindness. The results showed that an unexpected stimulus belonging to the attended semantic category but not sharing physical features with the attended stimuli was detected more often than a semantically unrelated stimulus. This effect was larger when the unexpected stimuli were words than when they were pictures. The results imply that the semantic relation between the observer's attentional set and the unexpected stimulus plays a crucial role in inattentional blindness: An unexpected stimulus semantically related to the observer's current interests is likely to be seen, whereas unrelated unexpected stimuli are unseen. Attentional selection may thus be driven by purely semantic features: Meaning may determine whether or not one sees a stimulus.

Different cognitive processes underlying human mate choices and mate preferences

Starting with the assumption that the underlying function of mate choice is reproductive success, evolutionary psychologists have proposed that men should seek young, fertile, faithful women, and women should seek high-status, resourceful, committed men. This evolutionary reasoning predicts what traits people will actually tend to choose, but not necessarily what people say they will (or would like to) choose. Todd et al. suggest that different cognitive processes underlie mate preferences and actual human mate choices. Here is their abstract:

Based on undergraduates' self-reports of mate preferences for various traits and self-perceptions of their own levels on those traits, Buston and Emlen [Buston PM, Emlen ST (2003) Proc Natl Acad Sci USA 100:8805–8810] concluded that modern human mate choices do not reflect predictions of tradeoffs from evolutionary theory but instead follow a "likes-attract" pattern, where people choose mates who match their self-perceptions. However, reported preferences need not correspond to actual mate choices, which are more relevant from an evolutionary perspective. In a study of 46 adults participating in a speed-dating event, we were largely able to replicate Buston and Emlen's self-report results in a pre-event questionnaire, but we found that the stated preferences did not predict actual choices made during the speed-dates. Instead, men chose women based on their physical attractiveness, whereas women, who were generally much more discriminating than men, chose men whose overall desirability as a mate matched the women's self-perceived physical attractiveness. Unlike the cognitive processes that Buston and Emlen inferred from self-reports, this pattern of results from actual mate choices is very much in line with the evolutionary predictions of parental investment theory.

Thursday, October 04, 2007

Cortical evolution and skilled hand use.

Unlike other New World species, such as squirrel monkeys, that exclusively use a power grip, cebus monkeys frequently use a precision grip in which the thumb and forefinger are brought into contact with one another to manipulate small objects, or engage in goal-directed tool use. Such a precision grip is observed in many old world monkey species, such as the macaques. Padberg et al. find:

..Unlike other New World Monkeys, but much like the macaque monkey, cebus monkeys possess a proprioceptive cortical area 2 and a well developed area 5, which is associated with motor planning and the generation of internal body coordinates necessary for visually guided reaching, grasping, and manipulation.
This is an example of parallel evolution:
...The similarity of these fields in cebus monkeys and distantly related macaque monkeys with similar manual abilities indicates that the range of cortical organizations that can emerge in primates is constrained, and those that emerge are the result of highly conserved developmental mechanisms that shape the boundaries and topographic organizations of cortical areas.
Left, Primate cladogram showing which primate taxa have the following characteristics related to manual control: complex manipulation (e.g., grasping food with one hand and peeling it with the other), use of feeding tools, corticospinal (CS) terminals in ventral horn (VH), opposable (or laterally opposable) thumb, and presence of parietal area 2. Filled box, Characteristic is present. Unfilled box: characteristic has been sufficiently tested and is absent. Right, Parietal areas and representative grasp postures traced from photographs in five primate species.
[Note: pink and green indicate areas 2 and 5 mentioned above.)